The invention relates to a process for producing very fine polymer fibres of finite length having an average fibre diameter of 0.1 to 10 .mu.m, preferably 0.1 to 4 .mu.m, from thermoplastic polymers. The basis of the process is whirling the molten polymer radially out of a rotating nozzle head through a plurality of exit holes with fibre formation and depositing the fibres formed on a collecting surface in web form.
Such whirler or centrifugal spinning processes are known and described for example in U.S. Pat. No. 4,277,436, U.S. Pat. No. 4,237,081, FR No. 1,298,508 and DE No. 3,105,784. More particularly, in the centrifugal spinning process of DE No. 3,105,784 use is made of an axially flowing cooling medium which cools the fibres formed and the spinning element. Consequently, this process is naturally only suitable for low-melting polymers of low viscosity. To avoid an excessively low pressure in the centre of the centrifugal field and the consequent aspiration of the fibres formed, it is necessary to employ comparatively low cooling air speeds. The cooling medium cannot therefore be used at the same time for stretching and drawing the fibres (attenuation).
Furthermore, EP No. 0,168,817 describes a centrifugal spinning process where the melt is evidently introduced under pressure into a nozzle rotating at relatively low circumferential speed. This makes it possible to produce relatively coarse filaments in a continuous manner. No drawing of the filaments by a dynamic gas effect going beyond the centrifugal attentuation takes place.